Spark-plug



SPARK Puis.

Patented Ot. 25, 1921.

UNITED STATES PATENT OFFICE.

TO ALLEN SPECIALTY COM- PANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

SPARK-PLUG.

Specification of Letters Patent.

Patented Oct. 25, 1921.

Application filed May 17, 1920. Serial No. 381,934.

To all 'whom it may eminem:

13e it known that I, OGLESBY ALLEN, Jr., a citizen of the United States, and a resident of Chicago` in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Spark-Plugs; and I do hereby declare that the following is a tull, clear, and exact description thereot, reference being had to the accompanying drawings, and to the characters of ret'- erence marked thereon, which form a part ot this specification.

This invention relates to improvements in spark or ignition plugs for the ignition systems or' explosion engines, and the invention consists in the combination and arrangement of the parts shown in the drawings and described in the specification, and is more particularly pointed out in the appended claims.

Among the objects of the invention is to provide a spark plug which is made of few rugged and durable parts which are simple to construct and assemble, and which mayv be made at a. relatively low cost as compared to the ei'liciency of the plug.

Another object of the invention is to produce a spark plug which does not foul in operation in a manner to short circuit above the arcing points ofthe terminals, and in this respect to provide means associated with the live terminal above the sparking point thereof which acts as a heat retainer on the live terminal for the double'purpose of retaining heat thereat to avoid clinging of carbon thereto, said heat retainer being of a material to avoid the deposit of carbon thereon.

A further object of the invention is to provide a construction and arrangement of the shell and porcelain insulatorwhich will permit the insulator to be made relatively short so as to keep it away from the carbon depositing zone, and which, at the same time materially reduces the cost of the insulator.

A further object of the invention is to improve the construction and arrangement oi' the grounded terminals, and especially of that type where twin grounded terminals are employed.

As shown in the drawings,

Figure 1 is a side elevation of a spark plug embodying my invention.

Fig. 2 is an axial section thereof, with parts in elevation.

Figs. 3 and l are cross sections on the respective lines 3-3 and 4 4 of Fig. 2.

Fig. 5 is a bottom end view of the pluO.

As shown in said drawings,-

10 designates the metal shell of the plug, 11 the porcelain, or other insulator, therein and extending upwardly from the top of the shell, 12 a rod which extends through an axial opening in the insulator and upwardly above the same, and extends below said insulator and the shell to constitute the live terminal 18 of the plug. Said rod is threaded and is held in place between a collar 111A at the lower end of the insulator and a nut 15 threaded to the rod above the insulator that bears against an insulating washer 16 that lies u on the upper end of the insulator. A t readed cap nut 17 engages the threaded rod above the nut 15 to act with the nut 15 as a binding screw for a circuit wire at one side of the ignition circuit. 18

eesignates the grounded terminals, there being two in the construction shown arranged symmetrically with respect to the live terminal 13.

The shell has an enlarged bore open at its top to receive a cylindric enlargement 2() of the insulator, providing thereon upwardly and downwardly facing shoulders to oppose a shoulder 21 in the shell and the lower end of a nut 22 that enters the enlarged bore of the shell and is threaded thereto. Thus the insulator is held `from axial displacement in the shell. Yielding washers are interposed between said shoulders on the insulator and the shoulder 21 and lower end of the nut 22 to avoid straining the insulator in a manner to check the' same. The lower end of the shell is reduced and exteriorly threaded, and said reduced portion of the shell has a relatively small diameter bore to constitute achamber 23 in which the collar 14 is inclosed. The grounded terminals are made integral parts of the lower reduced end of the shell and are disposed on the circle of the shell 180 degrees 'lhe collar lilis threaded on the rod 12 and is spaced Jfrom the lower end of the porcelain insulator by an insulating washer 280i substantial thickness. Y bears Vat its lowerl end on a shoulder 29 formed, preferably, integral with the'rod 12,

so that said collar is confined between said shoulder 29 andthe lower end of the porcelain. l f f f The said collar isV made-of a-material that will receive av high polish and one which will also retain heat, brass being a suitable material. flt is of general inverted conical shape, so thatiat its lower endit is farthestremoved from the wall ofthe reduced part of the shell, which wall may, andv preferably will, be made quite thin. l have found that such a material as brass` when polishedA and under the Vtempelrature to which it will be subjected in operation of the plugtends to reject carbon deposit andis readily maintained un- 'ouled over a long period or' time. Moreover there interposed between the upper larger end of the collar and the lower end of the insulator, which is tapered at Vsaid lower end with a terminal diameter not greater than the base of thekconical collar and its associated insulatingl washer 28, which said insulating washer has the eieet to prevent leakage of current from the collar to any cai'- bon deposit on the lower tapered end of the porcelain and thence to the `rounded shell, the insulating washer 28 serving as a barrier against suoli leakage. Moreover the tapering of the lower endl of the insulator serves further to minimize leakage of current from the collar 14 to the shell, Vbecause whatever carbon may lodgev on the lower tapered end of the insulator is spaced a safe dlstance from the shell, even though there is a tendency to leakage from the collar 14 to carbon deposit on said'tapered vend of the insulator, and the barrier between the upper larger end of the The said collar f collar 14 and carbon deposit at the full diameter of the insulator is sufficiently great to be safe.

It will thus be seen that the entire arrangement or" the parts within the thin walled low-er part Vof the shell goes toward barrier interference betweenV the live termnal and the metal parts associated therewith above the sparking point of the terminals, so that sparking between the intended points or lines of the terminals is insured; and further that said arrangement is such as to maintain said parts free from leakage over relatively long periods of time. Thus thereV is assured great saving oi' time in keeping the spark alu@ in (rood tiring condition and is also assured full snappy sparks that will lignite the compressed charges to the best advantage, and thereby avoid wastage of fuel due to defective Yor non-sparking. Y

' lt will also be noted that a spark plug possessing these advantages is simple`,'is rugged and long lived and can be made at small cost.

l claim as my invention.

l. A spark plug, comprising a shell, an insulatorV within said shell and terminatingv above thev inner end tl ereo, so that an open chamber is Yleft at the inner end of the shell, a terminal rod extending throughsaid insulator and projecting beyond the inner end of the shell, and an inwardly tapering or conical metallic carbon-rejecting element surround ing said terminal, said element having greater heat conductivity than said terminal" and having a highly polishedsurface.

2. ln'a'spark plug as set forth in claim 1, an insulating washer interposed between said metallic element and said insulator, said washer having a diameter not less than the base of said conical element, and being of substantial thickness to thereby serve as a barrier to prevent leakage due to any carbon deposit between the inner end of the insulator and the adjacent base orp'said conical metallic element. f f

VIn witness whereof I claim the 'foregoing' as my invention, hereunto append my sig nature this 11th day of May, 1920.

oeLrisBv ALLEN, Ja. 

